We present an inquiry-based lab approach that enabled undergraduate students to synthesize ruby and sapphire gemstones not only as nanocrystals but also as macroscopic crystals through assisted microwave combustion synthesis and a flux growth method. This approach is highly involving for the students and can be used as a support to easily train them on more theoretical knowledge such as spectroscopy, light properties (e.g., light scattering), binary diagrams, etc. and connect them to laboratory experiments. The trial-and-error process that led to the final procedure was spread over a few years and showed how involvement, imagination, and curiosity can remain high even in a multiyear process involving different generations of students.